Blair Amy C, Hufbauer Ruth A
Graduate Degree Program in Ecology and Department of Bioagricultural Sciences and Pest Management, Colorado State University Fort Collins, CO, USA.
Graduate Degree Program in Ecology and Department of Bioagricultural Sciences and Pest Management, Colorado State University Fort Collins, CO, USA ; Centre de Biologie et Gestion des Populations Campus International de Baillarguet CS 30016, Montferrier-sur-Lez cedex, France.
Evol Appl. 2010 Jan;3(1):40-51. doi: 10.1111/j.1752-4571.2009.00097.x. Epub 2009 Aug 27.
Hybridization has been hypothesized to influence invasion through the generation of novel phenotypes and/or increased levels of genetic variance. Based on morphology, hybrids between diffuse knapweed and spotted knapweed, two invasive plants in North America, are present in the invaded range. Some individuals within most diffuse knapweed sites in North America exhibit intermediate diffuse × spotted floral morphology. We examined hybridization at the molecular level, using amplified fragment length polymorphisms. Approximately a quarter of the assayed North American diffuse knapweed individuals exhibited evidence of introgression from spotted knapweed. However, plants with intermediate morphology did not show evidence of mixed ancestry more often than the plants with typical diffuse knapweed morphology. The high proportion of hybrid individuals in North American diffuse knapweed sites found here, combined with evidence from recent studies, suggests that diffuse knapweed was likely introduced with admixed individuals, and the hybrids are not newly created postintroduction. A century of backcrossing with diffuse knapweed has likely decoupled the relationship between morphology and admixture at the molecular level. In contrast to the scenario encountered in North America, in the native range where diploid diffuse and spotted knapweed overlap, hybrid swarms are common. In such sites, the floral phenotype aligns more closely with the genotype.
有人提出，杂交可能通过产生新的表型和/或增加遗传变异水平来影响入侵。基于形态学，北美两种入侵植物——扩散矢车菊和斑点矢车菊之间的杂交种存在于入侵范围内。北美大多数扩散矢车菊分布地的一些个体呈现出扩散矢车菊×斑点矢车菊的中间花形态。我们使用扩增片段长度多态性在分子水平上研究了杂交情况。大约四分之一被检测的北美扩散矢车菊个体显示出有来自斑点矢车菊的渐渗迹象。然而，具有中间形态的植株并不比具有典型扩散矢车菊形态的植株更常表现出混合血统的证据。此处发现的北美扩散矢车菊分布地中杂交个体的高比例，加上近期研究的证据，表明扩散矢车菊可能是与混交个体一起被引入的，而且这些杂交种并非在引入后新产生的。与扩散矢车菊一个世纪的回交可能在分子水平上使形态与混合血统之间的关系解耦。与在北美遇到的情况相反，在二倍体扩散矢车菊和斑点矢车菊重叠的原生范围内，杂交群体很常见。在这些地方，花的表型与基因型的匹配度更高。
